MdePkg BaseLib NASM Thunk16: Remove remaining 'DB' code

Convert remaining 'DB' code to assembly code by:
* Move instruction immediate data labels to end of instruction
* Use strict keyword to make sure immediate data size is not optimized

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16024 6f19259b-4bc3-4df7-8a09-765794883524

1 files changed, 23 insertions, 24 deletions

diff --git a/MdePkg/Library/BaseLib/Ia32/Thunk16.nasm b/MdePkg/Library/BaseLib/Ia32/Thunk16.nasm
index a1093e0107..c08e41de9d 100644
--- a/MdePkg/Library/BaseLib/Ia32/Thunk16.nasm
+++ b/MdePkg/Library/BaseLib/Ia32/Thunk16.nasm
@@ -59,7 +59,7 @@ SECTION .data
 ; These are global constant to convey information to C code.

 ;

 ASM_PFX(m16Size)         DW      InternalAsmThunk16 - ASM_PFX(m16Start)

-ASM_PFX(mThunk16Attr)    DW      _BackFromUserCode.ThunkAttr - ASM_PFX(m16Start)

+ASM_PFX(mThunk16Attr)    DW      _BackFromUserCode.ThunkAttrEnd - 4 - ASM_PFX(m16Start)

 ASM_PFX(m16Gdt)          DW      _NullSegDesc - ASM_PFX(m16Start)

 ASM_PFX(m16GdtrBase)     DW      _16GdtrBase - ASM_PFX(m16Start)

 ASM_PFX(mTransition)     DW      _EntryPoint - ASM_PFX(m16Start)

@@ -94,8 +94,8 @@ o32 call    dword .Base                 ; push eip
     push    es

     push    ds

     pushad

-    DB      66h, 0bah                   ; mov edx, imm32

-.ThunkAttr: dd   0

+    mov     edx, strict dword 0

+.ThunkAttrEnd:

     test    dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15

     jz      .1

     mov     ax, 2401h

@@ -116,18 +116,18 @@ o32 call    dword .Base                 ; push eip
     mov     bx, [bp - IA32_REGS.size + IA32_REGS._EIP]

     shl     eax, 4                      ; shl eax, 4

     add     ebp, eax                    ; add ebp, eax

-    DB      66h, 0b8h                   ; mov eax, imm32

-.SavedCr4:  DD      0

+    mov     eax, strict dword 0

+.SavedCr4End:

     mov     cr4, eax

 o32 lgdt [cs:bx + (SavedGdt - .Base)]

-    DB      66h, 0b8h                   ; mov eax, imm32

-.SavedCr0:  DD      0

+    mov     eax, strict dword 0

+.SavedCr0End:

     mov     cr0, eax

-    DB      0b8h                        ; mov ax, imm16

-.SavedSs    DW      0

+    mov     ax, strict word 0

+.SavedSsEnd:

     mov     ss, eax

-    DB      66h, 0bch                   ; mov esp, imm32

-.SavedEsp   DD      0

+    mov     esp, strict dword 0

+.SavedEspEnd:

 o32 retf                                ; return to protected mode

 

 _EntryPoint:

@@ -155,15 +155,14 @@ BITS    16
     mov     gs, cx

     mov     cr0, eax                    ; real mode starts at next instruction

                                         ;  which (per SDM) *must* be a far JMP.

-    DB      0eah

-.RealAddr: DW 0, 0

-

+    jmp     0:strict word 0

+.RealAddrEnd:

     mov     cr4, ebp

     mov     ss, si                      ; set up 16-bit stack segment

     xchg    esp, ebx                    ; set up 16-bit stack pointer

     mov     bp, [esp + IA32_REGS.size]

-    mov     [cs:bp + (_BackFromUserCode.SavedSs - _BackFromUserCode)], dx

-    mov     [cs:bp + (_BackFromUserCode.SavedEsp - _BackFromUserCode)], ebx

+    mov     [cs:bp + (_BackFromUserCode.SavedSsEnd - 2 - _BackFromUserCode)], dx

+    mov     [cs:bp + (_BackFromUserCode.SavedEspEnd - 4 - _BackFromUserCode)], ebx

     lidt    [cs:bp + (_16Idtr - _BackFromUserCode)]

 

     popad

@@ -224,28 +223,28 @@ BITS    32
     rep     movsd                       ; copy RegSet

     mov     eax, [esp + 40]             ; eax <- address of transition code

     mov     esi, edx                    ; esi <- 16-bit stack segment

-    lea     edx, [eax + (_BackFromUserCode.SavedCr0 - ASM_PFX(m16Start))]

+    lea     edx, [eax + (_BackFromUserCode.SavedCr0End - ASM_PFX(m16Start))]

     mov     ecx, eax

     and     ecx, 0fh

     shl     eax, 12

     lea     ecx, [ecx + (_BackFromUserCode - ASM_PFX(m16Start))]

     mov     ax, cx

     stosd                               ; [edi] <- return address of user code

-    add     eax, _ToUserCode.RealAddr + 4 - _BackFromUserCode

-    mov     [edx + (_ToUserCode.RealAddr - _BackFromUserCode.SavedCr0)], eax

-    sgdt    [edx + (SavedGdt - _BackFromUserCode.SavedCr0)]

+    add     eax, _ToUserCode.RealAddrEnd - _BackFromUserCode

+    mov     [edx + (_ToUserCode.RealAddrEnd - 4 - _BackFromUserCode.SavedCr0End)], eax

+    sgdt    [edx + (SavedGdt - _BackFromUserCode.SavedCr0End)]

     sidt    [esp + 36]        ; save IDT stack in argument space

     mov     eax, cr0

-    mov     [edx], eax                  ; save CR0 in _BackFromUserCode.SavedCr0

+    mov     [edx - 4], eax                  ; save CR0 in _BackFromUserCode.SavedCr0End - 4

     and     eax, 7ffffffeh              ; clear PE, PG bits

     mov     ebp, cr4

-    mov     [edx + (_BackFromUserCode.SavedCr4 - _BackFromUserCode.SavedCr0)], ebp

+    mov     [edx + (_BackFromUserCode.SavedCr4End - 4 - _BackFromUserCode.SavedCr0End)], ebp

     and     ebp, ~30h                ; clear PAE, PSE bits

     push    10h

     pop     ecx                         ; ecx <- selector for data segments

-    lgdt    [edx + (_16Gdtr - _BackFromUserCode.SavedCr0)]

+    lgdt    [edx + (_16Gdtr - _BackFromUserCode.SavedCr0End)]

     pushfd                              ; Save df/if indeed

-    call    dword far [edx + (_EntryPoint - _BackFromUserCode.SavedCr0)]

+    call    dword far [edx + (_EntryPoint - _BackFromUserCode.SavedCr0End)]

     popfd

     lidt    [esp + 36]        ; restore protected mode IDTR

     lea     eax, [ebp - IA32_REGS.size] ; eax <- the address of IA32_REGS